1. Field of the Invention
The present invention relates to an electronic component and a manufacturing method thereof, and more particularly, to a surface mounting type electronic component which is a complex module of a high frequency band required to be covered with a shield case such as a portable telephone, a VCO (Voltage Controlled Oscillator) of communication equipment, a PLL (Phase-Locked Loop) synthesizer module, a filter, a duplexer and an RF power amplifier, and the present invention also relates to a manufacturing method of such an electronic component.
2. Description of the Related Art
In recent years, as penetration of portable telephone, cordless telephone and the like increases, in order to miniaturize these radio communication apparatuses and to lower prices thereof, research has been done, as one of objects therefor, for reducing a size, lowering prices and enhancing a performance of a surface mounting type electronic component which is a complex module required to be covered with a shield case such as a VCO, an RF power amplifier and the like. Such an electronic component is required to be miniaturized, and a mounting structure of the shield case is large and a size of the electric component is influenced by the mounting structure. Further, the price of the electric component is largely influenced by the mounting structure and a mounting method of the shield case.
FIG. 3 is a partially broken perspective view for explaining one example of the VCO and a manufacturing method hereof (see Utility Model Registration Application Laid-open No. 5-21446). The VCO 200 comprises a component-mounting substrate 220, components 240 and a shield case 210. The components 240 are mounted inside a component-mounting surface 227 of the component-mounting substrate 220, a mounting electrode 222 for the shield case 210 is disposed on an outer periphery of the component-mounting substrate 220, and terminal electrodes 226 are disposed on a back surface 229 of the component-mounting substrate 220. A shield case edge 212 for substrate mounting is formed on the shield case 210. A solder 230 is formed on the shield case-mounting electrode 222 of the component-mounting substrate 220 by printing and forming the solder 230 on the shield case-mounting electrode 222 at the same time when solder for mounting the components 240 is printed, and thereafter melting and solidifying the solder 230 when the components 240 are mounted. This VCO 200 is produced by dividing a sheet substrate for producing a large number of pieces, i.e., the sheet substrate having a plurality of the component-mounting substrates 220, into each of the component-mounting substrates 220, then melting again the solder 230 on the component-mounting substrate 220 using an exclusive apparatus, and soldering the shield case edge 212 to the shield case-mounting electrode 222 on the component-mounting substrate 220.
FIG. 4 is a partially broken perspective view for explaining another example of a VCO and a manufacturing method thereof. The VCO 300 comprises a component-mounting substrate 320, components 340 and a shield case 310. There is no shield case-mounting electrode 222 on the component-mounting surface 227 of the component-mounting substrate 220 shown in FIG. 3, and this is a mounting method of the shield case suitable for miniaturizing. Shield case-mounting electrodes 322 and end surface electrodes 326 are formed on side surfaces 321 of the component-mounting substrate 320, and the shield case pawls 312 for substrate mounting are formed on lower portions of the shield case 310. The components 340 are mounted on a component-mounting surface 327 of the component-mounting substrate 320. This VCO 300 is produced by dividing a sheet substrate having a plurality of the component-mounting substrates 320 into each of the component-mounting substrates 320, thereafter covering the component-mounting substrate 320 with the shield case 310 from the side of the component-mounting surface 327, and fixing the shield case pawls 312 to the shield case-mounting electrodes 322 of the component-mounting substrate 320 with solder 330 using a soldering iron, an exclusive soldering robot or the like.
FIG. 5 is an exploded view for explaining still another example of a VCO and a manufacturing method thereof (see journal technical disclosure No. 94-20470 issued by Japan Institute of Invention and Innovation). The VCO 400 comprises a component-mounting substrate 420, components 440 and a shield case 410. The components 440 are mounted on a component-mounting surface 427 of the component-mounting substrate 420. In side surfaces 421 of the component-mounting substrate 420, shield case-mounting electrodes 422 are formed as end surface electrodes in side surfaces of 3/4 divided through holes 424 each obtained by dividing a elongated through hole into 3/4. Terminal electrodes 426 are also formed in the side surfaces 421 of the component-mounting substrate 420. Shield case pawls 412 whose central portions are expanded are formed on lower portions of the shield case 410. This VCO 400 is produced by pressing under pressure the shield case pawls 412 into the shield case-mounting electrodes 422 from the side of the component-mounting surface 417 on which the components 440 are mounted, thereby fixing the shield case 410 and the component-mounting substrate 420 to each other without soldering. This technique contributes to miniaturization, because the shield case-mounting electrodes are not disposed on the component-mounting surface 427 of the component-mounting substrate 420. Further, there is a feature that a soldering step and a cleaning step are unnecessary.
According to the method shown in FIG. 3, since the shield case-mounting electrode 222 must be disposed on the outer periphery of the component-mounting surface 227 of the component-mounting substrate 220, this is not suitable for miniaturization. Further, the solder 230 on the shield case-mounting electrode 222 is printed and formed at the same time when the solder for mounting the components 240 is printed. Therefore, the solder 230 is once melted when the components 240 are mounted and flux in the solder is not in active state and thus, it is necessary to improve the wettability of the solder by solder-plating on the lower surface of the shield case edge 212 of the shield case 210 in an actual case, and the price is increased accordingly. Further, there is a problem that it is necessary to use the exclusive apparatus for soldering the shield case-mounting electrode 222 and the shield case edge 212 of the shield case 210, and the price is further increased accordingly. Furthermore, according to such a structure, since the shield case must be mounted after the sheet substrate having the plurality of component-mounting substrates 220 is divided into each of the component-mounting substrates 220, this is not suitable for rationality such as a collective production in a state of the sheet substrate.
According to the method shown in FIG. 4, as the method shown in FIG. 3, after the sheet substrate having the plurality of component-mounting substrates 320 is divided into each of the component-mounting substrates 320, the shield case-mounting electrodes 322 and the shield case pawls 312 are soldered to each other on the side surfaces 321 of the component-mounting substrate 320, and this is not suitable for rationality. Further, if the number of the shield case pawls 312 and the number of the shield case-mounting electrodes 322 of the component-mounting substrate 320 are increased so as to strengthen the shielding properties, working time is increased accordingly. Furthermore, there is a problem that the price is increased if the exclusive soldering robot is employed. Further, since soldering is carried out after the substrate is divided, there is a problem that solder comes out from an outside shape of the product and thus, the product can not be miniaturized accordingly.
According to the method shown in FIG. 5, since the shield case pawls 412 are simply pressed and fitted under pressure into the 3/4 divided through holes 424 in which the shield case-mounting electrodes 422 are formed, the reliability of mounting and connection of the shield case pawls 412 is inferior. Further, the smaller the product (VCO 400 which is a surface mounting type electronic component) becomes, the greater the ratio of the product occupied by the 3/4 divided through holes formed in the side surfaces and therefore, this is not suitable for miniaturization. Furthermore, even if a diameter of each of the 3/4 divided through holes is reduced excessively or unreasonably to reduce the size of the shield case pawls 412, they can not be well fitted under pressure to each other because of the working precision, and a phenomenon that the shield case pawls 412 are not contacted with the shield case-mounting electrodes 422 well is generated.